Image optimization during facial recognition

ABSTRACT

Described is a technique for optimizing an image for facial detection. More specifically, described is a process of predicting the location of a face within an image and adjusting image settings based on at least a portion of the predicted location of the face. An image may be adjusted based on the characteristics of a metering region, which may be selected prior to performing facial detection. For example, the metering region may be a specified shape with dimensions equal to a certain percentage of the input image and placed at a specified location. The result of using such a metering region is that the image adjustments may be based on a portion of the face, and therefore, may be optimized for facial detection.

BACKGROUND

Devices with a built-in camera may have the ability to authenticate auser by performing facial recognition. Facial recognition methods oftenprocess an image in two steps. The first step, which may be described asdetection, locates a face within an image. The second step, which may bedescribed as recognition, analyzes the detected face to determine asimilarity between the detected face and a stored face or template. Toachieve accurate results, the facial recognition processes may dependupon the quality of detected images. When capturing images, a camera mayautomatically adjust capture settings based on image characteristics.These settings may include automatic adjustments to exposure and/orgain. For example, when an image condition includes a face with strongbacklighting, the automatic adjustment may reduce exposure in the imageto account for the backlighting. These image settings, however, may beoptimized for capturing the most visually appealing pictures.

BRIEF SUMMARY

In an implementation, described is a method of optimizing a capturedimage for facial detection. In response to receiving an indication toperform facial detection, a metering region within a portion of thecaptured image may be selected. The metering region may be based on anexpected location of a face and may be selected prior to detecting aface within the image. The image may be adjusted based on the meteringregion and a face may be detected within the adjusted image. The imagemay be optimized by adjusting an exposure, and/or another settingincluding an automatic gain control (AGC), contrast, saturation, and thelike.

In an implementation, a captured image may be optimized based on apredefined and static metering region. The metering region may bedescribed based on a size. The size of the metering region may bedescribed as being within a percentage range of the image. The meteringregion may also be described based on a relative location within theimage. For example, the metering region may be centered, within aspecified portion of the image, or include at least two quadrants of theimage.

In an implementation, described is a facial detection method includingexecuting a facial detection algorithm on a captured image a first timeand determining that a face is not detected within the image. A meteringregion within a portion of the image may be selected and the image maybe adjusted based on the metering region. The facial detection algorithmmay execute on the adjusted image a second time and may detect a face.The first execution may be based on a metering region of the entireimage and the second execution may be based on a metering regionoptimized for facial detection.

In an implementation, described is a device for optimizing an image forfacial detection. The device may include a camera for capturing theimage, a display previewing the captured image, and a processor foradjusting the captured image based on a metering region within a portionof the image. The processor may adjust the camera based on a meteringregion and a face may be detected based on the adjusted image. A previewof the captured image may be displayed and the metering region may bebased on a positioning guide displayed on the previewed image. Thedisplay may be a touch sensitive display and the metering region may bebased on a user input touching a portion of the previewed image.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosed subject matter, are incorporated in andconstitute a part of this specification. The drawings also illustrateimplementations of the disclosed subject matter and together with thedetailed description serve to explain the principles of implementationsof the disclosed subject matter. No attempt is made to show structuraldetails in more detail than may be necessary for a fundamentalunderstanding of the disclosed subject matter and various ways in whichit may be practiced.

FIG. 1 shows a simplified functional block diagram of a representativedevice according to an implementation of the disclosed subject matter.

FIG. 2 shows a flow diagram of optimizing an image for facial detectionaccording to an implementation of the disclosed subject matter.

FIG. 3 shows a flow diagram of performing facial detection a first andsecond time according to an implementation of the disclosed subjectmatter.

FIG. 4 shows an example of a metering region within a central portion ofthe image according to an implementation of the disclosed subjectmatter.

FIG. 5 shows an example of a metering region including two quadrants ofthe image according to an implementation of the disclosed subjectmatter.

FIG. 6A shows an example of an underexposed face within an image asdescribed in the disclosed subject matter.

FIG. 6B shows an example of a metering region within the image shown inFIG. 6A according to an implementation of the disclosed subject matter.

FIG. 6C shows an example of an adjusted image based on the meteringregion shown in FIG. 6B according to an implementation of the disclosedsubject matter.

DETAILED DESCRIPTION

Described is a process of improving facial detection in an image byadjusting image settings. Implementations describe adjusting the imagesettings based on a metering region that optimizes the image fordetecting a face. The metering region may use a relevant subset of theimage and may be based on an expected location of at least a portion ofa face within the image. By positioning the metering region in anexpected location of a face, the metering region may be selected priorto actually detecting a face.

FIG. 1 shows a simplified functional block diagram of a representativedevice according to an implementation of the disclosed subject matter.The device 50 may include a bus 51, processor 52, memory 54, user input56, display 58, memory 54, communications circuitry 53, storage 57,coder/decoder (CODEC) 55, and a camera 59.

The device 50 may include or be part of a variety of types of devices,such as a mobile phone (including a “smartphone”), tablet computer,netbook, laptop, desktop, personal digital assistant (“PDA”), set-topbox, television, and/or watch, among others. The processor 52 may be anysuitable programmable control device and may control the operation ofone or more processes, such as the facial detection process as discussedherein, as well as other processes performed by the device 50.

The memory 54 may include one or more different types of memory whichmay be used for performing device functions. For example, the memory 54may include cache, ROM, and/or RAM. The bus 51 may provide a datatransfer path for transferring between components of the device 50. TheCODEC 55 may be included to process digital and analog audio and/orvideo signals to produce sound, voice, and multimedia. The display 58may provide visual output and may include a touch-sensitive screen.

The storage 57 may store multimedia (e.g. video, music, and photos,etc.), software (e.g., for implementing various functions on device 50),and any other suitable data. The storage 57 may include a storagemedium, such as a hard-drive, solid state drive, flash drive, and thelike. The storage 57 may be integral with the device 50 or may beseparate and accessed through an interface to receive a memory card, USBdrive, optical disk, and the like.

The user input 56 may allow a user to interact with the device 50. Forexample, the user input 56 may include buttons, a keypad, a touchscreen, and the like. The communications circuitry 53 may includecircuitry for wireless communications for short-range and/or long rangecommunication. For example, the wireless communication circuitry mayinclude Wi-Fi enabling circuitry for one of the 802.11 standards, andcircuitry for other wireless network protocols including Bluetooth, theGlobal System for Mobile Communications (GSM), and code divisionmultiple access (CDMA) based wireless protocols. Communicationscircuitry 53 may also include circuitry that enables the device 50 to beelectrically coupled to another device (e.g. a computer or an accessorydevice) and communicate with that other device.

The camera 59 enables the device 50 to capture still images, video, orboth. The camera 59 may capture an image or series of imagescontinuously, periodically, at select times, and/or under selectconditions. The camera 59 may be part of or coupled to one or both afront-facing camera or rear-facing camera of the device 50.

The device 50 may be battery-operated and portable so as to allow a userto communicate with others, listen to music, play games or video, recordvideo or take pictures, or control other devices. The device 50 may berelatively compact which enables a user to easily manipulate thedevice's position, orientation, and movement. Accordingly, the device 50may provide techniques of sensing such changes in position, orientation,and movement to enable a user to interface with or control the device 50by affecting such changes. Further, the device 50 may include avibration source, under the control of processor 52, for example, tofacilitate sending motion, vibration, and/or movement information to auser related to an operation of the device 50. Other devices orcomponents may be part of or connected to the device 50, and conversely,all of the components shown in FIG. 1 need not be present to practicethe present disclosure.

FIG. 2 shows a flow diagram of optimizing an image for facial detectionaccording to an implementation of the disclosed subject matter. In step22, the device 50 may capture an image with a camera 59. Typically, thecaptured image may be a live image that dynamically and continuouslycaptures an image within a field of view of the camera 59 in real-time.The captured image may also include a still image or single frame, forexample, when a snapshot or picture is taken. In addition, the capturedimage may also include a retrieved image that may be stored on thedevice 50. A preview of the captured image may be shown on a display 58in real-time or upon retrieval. Image capture may be initiatedautomatically, for example, upon a request to perform facial detectionand/or recognition, or it may be initiated manually by a user. The imagecapture may occur prior to or after receiving an indication to performfacial recognition.

In step 23, the device 50 may receive an indication to perform facialdetection. The indication for facial detection may be explicit orimplicit. An explicit request to perform facial detection may include auser selecting a facial detection setting on the device 50 for imagecapture. This selection may be made in real-time, for example, whilecapturing a live image, or prior to capturing an image such as settingan image capture preference (e.g. facial detection mode). The explicitindication may also include a request to perform an image adjustment forfacial detection and/or recognition on a stored image (e.g. a picture).An implicit indication may include initiating or requesting a processthat includes facial detection as a sub-process or step. For example, afacial recognition process may include performing an initial orconcurrent step of facial detection. The device 50 may have an accesscontrol feature that authenticates a user of the device by performingfacial recognition. Accordingly, the indication may include variousforms of a request for user authentication. Facial recognition as a formof authentication may be common for many applications in handhelddevices. Facial recognition is particularly convenient for devices witha front-facing camera because they may efficiently perform facialrecognition when a user is located in a position to view a display 58.The request for authentication may be automatic or may be initiatedmanually by the user. For example, the authentication request may occurupon a request to “unlock” the device from a “locked” state. This mayoccur automatically, for example, when the device 50 “awakens” from apowered-down or “sleep” state, or it may occur manually, for example, bydirect user input. The device 50 may include controlling user access atan application level. Accordingly, another example of direct user inputmay include launching an access controlled application to initiate anauthentication request.

In step 24, a metering region may be selected. The selection may be inresponse to the indication to perform facial recognition. The responsemay include an immediate response, or it may include a deferred responsethat may occur during the detection process. For example, upon receivingan indication that a facial detection process has been initiated, thedevice 50 may first activate the camera 59. Accordingly, the selectionof the metering region may be deferred until the camera 59 is activatedand initiates image capture. The selection of a metering region mayoccur without, or prior to, detecting a face within an image.Conventional facial recognition programs typically perform facialdetection first, and then optimize the image based on imagecharacteristics of the detected face. Facial detection methods mayinclude detecting a face based on a shape, skin color, relativepositioning of facial features, etc. In certain circumstances, however,the facial detection may not be possible. For example, when capturingimages, a camera may automatically adjust capture settings based oncharacteristics of the entire image. For example, these settings mayinclude automatic adjustments to exposure or other images settings.These image settings may be optimized for capturing the most visuallyappearing pictures. At this stage, these adjustments may not beoptimized for facial detection because a face has not been detected yet.For example, when an image condition includes a face with strongbacklighting, the automatic adjustment may reduce exposure in the imageto account for the backlighting. This adjustment may alter the image toa point where there is insufficient contrast in the region of the face.As a result, the device 50 may not be able to perform facial detection.

Implementations of the disclosed subject matter may optimize an imagewithout the requirement to perform facial detection. More specifically,implementations may select a metering region by predicting an expectedlocation of a face. Accordingly, the metering region may providecharacteristics of a portion face and not the entire image. For example,implementations may predefine the metering region to include a centralregion of a captured image. A user capturing an image of their face islikely to place their face within the center or close to the center of afield of view of a camera 59. Accordingly, there may be a highlikelihood that the metering region may include at least a portion ofthe user's face, and as a result, the image may be adjusted according toa more relevant subset of the image for facial detection. Thus, theimage may be optimized without, or prior to, performing facialdetection.

The metering region may be described relative to the captured image. Thecaptured image may be described in various manners including acoordinate space, quadrants, pixels values based on a resolution, zones,and the like. For example, using a coordinate space, the lower left mostpoint of the image may have a value of −1000, −1000, and the upper rightmost point may have a value of 1000, 1000. Accordingly, a center pointof the image would be 0, 0. A coordinate space may also be based onresolution. For example, a 1280×800 resolution screen may have 1, 1 (or0, 0) as the lower left most point and 1280, 800 as the upper right mostpoint. A metering region may be defined by its size, position, behaviorand other characteristics. The metering region may be described in termsof a percentage size of the image and a relative position. For example,the metering region may be centered within the image and have a size of20% of the image. In some cases, the metering region may be described asbeing within a portion of the image. A portion of the image is definedas an area less than the entire image. For example, a metering regionmay be within a central portion of the image. A central portion isdefined as a rectangular shape centered at the center point of the imageand may have a specified size. For example, using a coordinate space asdescribed above, a central portion with a size of 50% of the image mayhave a coordinate definition of −500, −500 as the lower left most pointand 500, 500 as the upper right most point of the rectangle. A meteringregion within this central portion may include the entire centralportion or may have a smaller area. A metering region within a portionof an image may not necessarily be rectangular in shape and may notnecessarily be centered at the center point of the portion of the image.

FIG. 4 shows an example of a metering region within a central portion ofthe image according to an implementation of the disclosed subjectmatter. As shown, metering region 40 may be within a portion of theimage 42. In this example, the portion of the image 42 may be describedas a central portion. As shown, the portion 42 is centered at a centerpoint (not shown) of the image. As with this example, although themetering region 40 is within a central portion of the image, it may notbe centered at the center point of the image. This offset may accountfor any bias that may occur. For example, a user may have a tendency toposition their face lower within the field of view of a camera 59.

The position of the metering region may also be described with respectto quadrants. For example, if a metering region is centered within theimage, it may include a portion of all four quadrants. If the meteringregion is centered only horizontally or vertically, it may only includea portion of a minimum of two quadrants.

FIG. 5 shows an example of a metering region including two quadrants ofthe image according to an implementation of the disclosed subjectmatter. As shown, the image may be divided in four equal quadrants,starting from the upper left most quadrant as quadrant 1 51, andclockwise to quadrant 2 52, quadrant 3 53, and quadrant 4 54. As shown,the metering region may include one or more quadrants. In this example,the metering region is centered horizontally within the image, and inthis instance, includes a portion of two quadrants (quadrant 3 53 andquadrant 4 54).

Typically, a metering region may be defined as a set of coordinates at aprogramming level. It should be noted that the above methods ofdescribing the location of the metering region and describing theorganization of the image may not be explicitly defined at a programminglevel. A person of ordinary skill in the art, however, would understandsuch descriptions and select a set of coordinates accordingly. Forexample, a description of a metering region with a size of 20% of theimage and within a central portion with a 50% size of the image, wouldenable a person of ordinary skill in the art to understand that theregion may be defined with a set of coordinates that need only be withinthe −500, −500 and 500, 500 rectangular boundary in the coordinate spaceas described above.

The metering region may also be described by its behavior. For example,the metering region may be static or dynamic. When the metering regionis static, the region does not necessarily track particular objectswithin the image. For example, with live images, objects may move withinthe image and these may or may not remain within the metering region.For instance, if a coordinate system is used, the coordinates of themetering region may remain static despite movement of objects within theimage. In contrast, when the metering region is dynamic, the meteringregion may track a particular object within the live image and thecoordinates of the metering region may adjust accordingly.

The metering region may also be predefined. For example, a set ofcoordinates defining the metering region may be set prior to capturingan image. Accordingly, the metering region may be positioned in aparticular region regardless of the characteristics of the capturedimage. As described above, the metering region may be based on anexpected location of a face. Typically, the expected location of a facecorresponds to a central portion of the image. This positioning may befurther refined by additional factors. These factors may includecharacteristics derived from preferences, usage history, probability,etc. For example, a usage history may determine that a user typicallyplaces the face within a lower portion of the image and not precisely ina central portion. Accordingly, the selection of the metering region maybe repositioned accordingly.

In implementations, the captured image may be displayed as a preview ona display 58 of the device 50. In these situations, a positioning guidemay be used to direct a user to position their face within a certainregion of a field of view of the camera 59. For example, a guide may bedisplayed on the previewed image and a user may alter the position ofthe device 50 and/or their face to position their face according to theguide. Accordingly, a metering region corresponding to the displayedguide may be used to adjust the image without actually detecting theface. In this instance, it is likely that a user cooperates andpositions their face according to the guide. In some cases, thepositioning guide may be dynamic and the metering region may dynamicallytrack the positioning guide. The positioning guide may include aboundary, cross-hairs, one or more boundary edges, a shape (e.g. circleor rectangle), shading, or any other form of displaying a guide on thepreviewed image.

The metering region may also be based on receiving a user input thatselects a portion of the captured image. The user input may include aninput from an input device or a touch on a on touch sensitive display.For example, a user may touch the display 58 at a location correspondingto the location of a face within a captured image. The touch may beregistered by the device 50 and a metering region may be selected basedon the location of the touch. This may be an effective technique whenperforming facial recognition on an image including multiple faces in alive image or a stored image.

The metering region may also be based on characteristics of the image.As described, a face may not necessarily need to be detected to select ametering region. The metering region may be based on a contrast level,saturation level, color, and other image characteristics. For example, aface in front of a strongly lit background may have a low contrastlevel. The low contrast level may be identified as a probable locationof a face, and accordingly, the metering region may be within this lowcontrast region. Similarly, a low saturation may be identified for ametering region. Other image characteristics may also be used todistinguish between regions or identify a region that may include aface. More than one metering region may be selected and they mayoverlap. The metering region may also be defined with a particularweighting of pixels within the image. For example, the weights ofoverlapping metering regions may be added. Unlike typical facialdetection processes, it may not be necessary to show an outline orboundary region of the metering region on a previewed image. Instead,the metering region and adjustment may be done transparently to theuser.

In step 25, the captured image may be adjusted based on characteristicsof the metering region. The adjustment may adjust a live image inreal-time or may adjust a picture that may be stored. For example, anadjustment to a live image may involve dynamically adjusting thecaptured image in response to real-time changes in the field of view ofthe camera 59. The adjusting may adjust capture settings of the camera59, or may adjust the characteristics of a frame, or a stored image(e.g. snapshot) after a picture is taken. The metering region maytypically correspond to at least a portion of a face within the imageeven when the face is not detected. Accordingly, the metering region maybe optimized based on the characteristics of a portion of a face. Theimage adjustments may include optimizing one or more image settings.These settings may include exposure, gain, color balance (includingwhite-balance), focus, contrast, (which may be expressed as a ratio ordynamic range), saturation, brightness, gamma, hue, sharpness, and thelike. In should be noted that these settings may be adjusted in an imageand would be readily understood by a person of ordinary skill in theart.

Typically, an exposure setting may be adjusted. An exposure setting maygenerally relate to camera exposure parameters, such as exposure time(e.g. shutter speed), gain, and/or f-number (e.g. relative aperture). Byadjusting the exposure setting, an optimum brightness may be achievedfor a face within the captured image. As described, the exposure may beoptimized based on a metering region which may be a subset of the image.Conventional metering may be optimized for capturing the most visuallyappearing pictures, and therefore, are based on metering an entireimage. Instead of metering an entire image, implementations may selectthe most relevant subset of the image for facial detection (e.g. atleast a portion of a face). Accordingly, these adjustments may notproduce the images most suitable for pictures as they may be optimizedfor facial detection. For example, the adjustment may adjust exposure toenhance contrast in a region of the image including a face (e.g.foreground), and as a result, it may oversaturate a background of theimage to a point where objects in the background may not be visible. Asmentioned above, other image settings may also be adjusted to optimizefacial recognition.

FIGS. 6A-6C show an example of adjusting an exposure setting of an imagebased on a metering region within a portion of the image according to animplementation of the disclosed subject matter. FIG. 6A shows an exampleof an underexposed face within an image. This may occur, for example,when an image condition includes strong backlighting (e.g. when thesubject has their back to a brightly lit window). An exposure setting,for example, may be based on an analysis of the entire image.Accordingly, when the image background is very bright this method mayset the exposure to low levels such that the background is below asaturation level. As a result, as shown in FIG. 6A, the face may bewithin a low contrast region 60. In these situations, there is ofteninsufficient contrast in the region of the face to perform detection.Accordingly, adjusting the image to such levels as shown in FIG. 6A mayprevent detection of the face within the image.

FIG. 6B shows an example of a metering region within a portion of theimage shown in FIG. 6A according to an implementation of the disclosedsubject matter. A metering region 40 may be within a portion of theimage and may correspond to an expected location of a face. For example,as shown, the metering region 40 may be a specified shape (e.g.rectangle) with dimensions equal to a certain percentage of the inputimage (e.g. a percentage of the image size) and placed at a specifiedlocation (e.g. center of the input image). The metering region 40 may bepredefined and set prior to actually detecting a face.

FIG. 6C shows an example of an adjusted image based on the meteringregion 40 of FIG. 6B according to an implementation of the disclosedsubject matter. The result of using the metering region 40 is that theimage adjustment to exposure may be based on a portion of the face, andtherefore, optimized for facial detection. As shown in this example, animage with strong backlighting may be optimized by adjusting theexposure setting resulting in oversaturating the background 62. As alsoshown, however, the contrast range in the area of the face may beimproved, and accordingly, the image may be optimized for facialdetection.

Returning to FIG. 2, in step 26, a face may be detected within theadjusted image. The facial detection method may include known methodsfor detection and be based one or more algorithms for identifyingshapes, skin tone, color, facial texture data, and facial featureswithin an image. As described above, a metering region may be selectedprior to facial detection. In other implementations, a metering regionmay be selected after a facial detection algorithm is performed.

FIG. 3 shows a flow diagram of performing facial detection a first andsecond time according to an implementation of the disclosed subjectmatter. In step 30, the device 50 may capture an image in a similarmanner as described in step 22 of FIG. 2. In step 31, a first meteringregion may be selected. The first metering region may be based on anentirety of an image. For example, a standard or default auto exposurealgorithm may be used, such as one that bases exposure parameters on amean, median, or weighted value of the brightness of the entire image.In step 32, the image may be adjusted based on the first meteringregion. This adjustment may be based on providing the most visuallypleasing images and may be a default setting, or a setting optimized fortaking pictures.

In step 33, facial detection may be executed a first time. Inimplementations, the facial detection in step 33 may occur withoutadjusting the image in steps 31 and 32. In step 34, it may be determinedthat a face is not detected when executing facial detection the firsttime as the image adjustment (if performed in steps 31 and 32) may nothave necessarily been optimized for facial detection. After it isdetermined that a face was not detected, a metering region may beselected in step 35 and the captured image may be adjusted in step 36 ina similar manner as described in steps 24 and 25 of FIG. 2 respectively.In particular, in steps 35 and 36, the image may be optimized for facialdetection. In step 37, the facial detection algorithm may execute asecond time and may detect a face within the image optimized for facialdetection. As described above, the first metering region may be based onthe entire image. The first metering region may also include a subset ofthe image. For example, a size of the first metering region may belarger than a size of the metering region within the portion of theimage of step 35. Accordingly, in this scenario, the metering region instep 35 may be reduced to provide more precision for facial detectionoptimization.

In implementations, once facial detection is performed, the device 50may perform facial recognition on the detected face. The recognitionprocess may include comparing the detected face to a stored template.For example, features of the detected face template may be comparedagainst the features of the stored reference template and a recognitionconfidence score may be determined. Upon a successful facial recognition(e.g. confidence score above a specified value), the device 50 mayidentify the face of the user. For example, upon the completion offacial recognition, a user's face may be authenticated and the devicemay be accessed or “unlocked” in response to the authentication request.

Implementations described herein may be included in an article ofmanufacture (e.g., one or more computer program products) having, forinstance, computer usable media. The media has embodied therein, forinstance, computer readable program code for providing and facilitatingthe capabilities described herein. The article of manufacture may beincluded as a part of a device or sold separately.

The flow diagrams described herein are just examples. There may bevariations to these diagrams or the steps (or operations) describedtherein without departing from the implementations described. Forinstance, the steps may be performed in a differing order, or steps maybe added, deleted or modified. Described herein, references to “oneimplementation,” “an implementation,” “an example implementation,” etc.,indicate that the implementation described may include a particularfeature, structure, or characteristic, but every implementation may notnecessarily include the particular feature, structure, orcharacteristic. Moreover, such phrases are not necessarily referring tothe same implementation. Further, when a particular feature, structure,or characteristic is described in connection with an implementation,such feature, structure, or characteristic may be included in otherimplementations whether or not explicitly described.

The foregoing description, for purpose of explanation, has beendescribed with reference to specific implementations. However, theillustrative discussions above are not intended to be exhaustive or tolimit implementations of the disclosed subject matter to the preciseforms disclosed. Many modifications and variations are possible in viewof the above teachings. The implementations were chosen and described inorder to explain the principles of implementations of the disclosedsubject matter and their practical applications, to thereby enableothers skilled in the art to utilize those implementations as well asvarious implementations with various modifications as may be suited tothe particular use contemplated.

The invention claimed is:
 1. A method for a device to perform facialdetection, comprising: capturing an image; executing a facial detectionalgorithm on the image a first time; determining that a face is notdetected within the image based upon the execution the first time;selecting a metering region within a portion of the image; adjusting theimage based on the metering region; and detecting a face by executingthe facial detection algorithm on the adjusted image a second time; andthe method further comprising selecting a first metering region andwherein the execution the first time is based on the first meteringregion and a size of the first metering region is larger than a size ofthe metering region within the portion of the image.
 2. The method ofclaim 1, wherein the selected first metering region is based on anexpected location of the face.
 3. The method of claim 1, wherein saidadjusting includes adjusting a setting of at least one of an automaticgain control (AGC), color balance, focus, contrast, saturation,brightness, gamma, hue, and sharpness.
 4. The method of claim 1, furthercomprising displaying a preview of the captured image and wherein thepreview includes a face positioning guide and the selected firstmetering region is based on a location of the positioning guide.
 5. Themethod of claim 1, further comprising displaying a preview of thecaptured image and receiving a user input selecting a portion of thepreviewed image and wherein the selected first metering region is basedon the received user input.
 6. The method of claim 1, further comprisingidentifying a low contrast region and wherein the selected firstmetering region is within the low contrast region.
 7. The method ofclaim 1, further comprising receiving a request to authenticate a faceof a user.
 8. The method of claim 1, wherein said adjusting includesadjusting an exposure setting.
 9. The method of claim 1, wherein theimage is a live image.
 10. The method of claim 1, wherein the meteringregion is centered within the image.
 11. The method of claim 1, whereinthe metering region size is greater than or equal to 5% of the imagesize and less than or equal to 50% of the image size.
 12. A deviceperforming facial detection, comprising: a camera for capturing animage; a display previewing the captured image; and a processorconfigured to: execute a facial detection algorithm on the image a firsttime; determine that a face is not detected within the image based uponthe execution the first time; select a metering region within a portionof the image; adjust the image based on the metering region; detect aface by executing the facial detection algorithm on the adjusted image asecond time; and select a first metering region and wherein theexecution the first time is based on the first metering region and asize of the first metering region is larger than a size of the meteringregion within the portion of the image.
 13. The device of claim 12,wherein the selected first metering region is static and determinedprior to said capturing the image.
 14. The device of claim 12, whereinthe display includes a face positioning guide on the previewed image andthe selected first metering region is based on a location of thepositioning guide.
 15. The device of claim 12, wherein the display istouch-sensitive and the selected first metering region is based on areceived location of a touch input to the previewed image.
 16. Thedevice of claim 12, wherein the processor is further configured toadjust the image based on the metering region by adjusting an exposuresetting.
 17. The device of claim 12, wherein the image is a live image.18. The device of claim 12, wherein the metering region is centeredwithin the image.
 19. The device of claim 12, wherein the meteringregion size is greater than or equal to 5% of the image size and lessthan or equal to 50% of the image size.
 20. A system comprising: one ormore computers and one or more storage devices storing instructionswhich, when executed by the one or more computers, cause the one or morecomputers to perform operations comprising: capturing an image;executing a facial detection algorithm on the image a first time;determining that a face is not detected within the image based upon theexecution the first time; selecting a metering region within a portionof the image; adjusting the image based on the metering region;detecting a face by executing the facial detection algorithm on theadjusted image a second time; and selecting a first metering region andwherein the execution the first time is based on the first meteringregion and a size of the first metering region is larger than a size ofthe metering region within the portion of the image.